# Limitations on Using Sync-diff-inspector

__*sync-diff-inspector limitations*__

+ Data types such as JSON, BIT, BINARY, BLOB, etc. are not supported
+ float types such as FLOAT and DOUBLE cannot be validated between TiDB and MySQL
+ Tables that do not contain primary keys or unique indexes can be validated, but repairing SQL may not repair data correctly
+ Data validation between MySQL and TiDB or between MySQL and MySQL does not support data synchronization online verification

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Online verification is not supported for data synchronization between MySQL and TiDB. It is necessary to ensure that no data is written to the upstream and downstream validation tables, or that the data in a certain range does not change. Configure range to verify the data in this range.

Data types such as JSON, BIT, BINARY, BLOB, etc. are not supported, and ignore-columns must be set to ignore checking these types of data during validation.

float types such as FLOAT and DOUBLE are implement differently in TiDB and MySQL. When calculating checksum, 6 and 15 significant numbers are taken respectively. If you do not use this feature, you need to set ignore-columns to ignore checks for these columns.

Validation is supported for tables that do not contain primary keys or unique indexes, but if the data is inconsistent, the SQL generated for repair may not repair data correctly.